Double line phenotypes in rabbit IgG allotypes and their relation to the cis/trans configuration of the IgG markers.

Rabbit antiallotype sera raised against heavy chain markers sometimes show double precipitin lines with all or some of the corresponding antigens (double and single line phenotypes). In a number of cases the double line phenotypes behave as alleles of the single line phenotypes and this feature allows a genetic and immunochemical analysis of these systems. In three cases that have been analysed, the double line phenotype arise when a precipitating a locus allotype and a non-precipitating d or e locus allotype are present on the same molecule (a1 and d14), (a1 and d11), (a3 and d11). This only happens when the corresponding genes are present on the same chromosome (cis configuration) of the diploid pair. These sera are therefore useful for determining directly the genotype of the animals.